1. Field of the Invention
This invention relates to a method of packing a liquid jet recording head to be used for printing by ejecting liquid droplets from ejection orifices onto a printing medium. The present invention also relates to a liquid jet recording head and a liquid jet recording apparatus equipped with such a liquid jet recording head.
2. Related Background Art
Conventional liquid jet recording apparatus comprise a carriage adapted to reciprocate in a direction almost perpendicular to the moving direction of the recording medium, and a liquid jet recording head is mounted on the carriage.
The liquid jet recording head comprises as principal components thereof a liquid jet section for ejecting liquid from its ejection orifices onto a recording medium for the purpose of recording and a liquid storage chamber containing liquid to be supplied to the liquid jet section. There are exemplified liquid jet recording heads that typically comprise a liquid storage section as an integral part thereof and can be replaced for the liquid jet recording apparatus on which they are mounted.
Such liquid jet recording heads are not adapted to be refilled with liquid when the liquid contained therein is used up. In other words, when the liquid initially contained in a liquid jet recording head is totally consumed, the latter is disposed as waste and a new one is mounted on the scanning carriage. With such an arrangement, the running cost of the liquid jet recording apparatus will be high particularly when the liquid jet recording head is replaced frequently.
On the other hand, there are exemplified liquid jet recording heads of the type designed to reduce the running cost and provided with a separate liquid storage section so that only the latter may be replaced when all the liquid contained in the section is consumed. There are also known liquid jet recording heads of the type provided with an external liquid storage chamber from which liquid is supplied to the liquid jet recording head. Liquid jet recording heads of these types are also designed to reduce the running cost.
In short, known liquid jet recording heads are classified into (1) those that are provided with a liquid storage chamber arranged in the inside of the liquid jet recording head, (2) those that are provided with a replaceable liquid storage chamber and (3) those that are supplied with liquid from a remote liquid storage chamber connected thereto typically by means of a pipe.
Regardless of the type of liquid jet recording heads, however, the internal pressure of the head is normally held to a level lower than the atmospheric pressure or to a negative pressure level relative to the outside of the head in order to prevent liquid from leaking out of the liquid jet recording head.
Now, some of the characteristic aspects of the negative pressure generating means of the liquid supply system of a liquid jet recording head of each of the above identified types will be discussed below.
In the case of a liquid jet recording head provided with a liquid storage chamber arranged in the inside thereof, the liquid storage chamber is normally equipped with a negative pressure generating means for maintaining the negative pressure in the liquid storage chamber. The negative pressure generating means may be a liquid absorbing means (liquid absorption system), a mechanical means or some other means.
A liquid absorption means is typically designed to utilize the capillary force of a porous liquid absorbing material such as urethane in order to maintain the negative pressure in the liquid storage chamber and, at the same time, retain the liquid therein. A mechanical means is typically adapted to utilize the resilient force of an elastic body so as to contract a flexible wall, thereby maintaining the negative pressure in the liquid storage chamber.
Now, a liquid jet recording head provided with a replaceable liquid storage chamber will be described below. A liquid absorption system is typically employed as negative pressure generating means in a liquid jet recording head provided with a replaceable liquid storage chamber. More specifically, such a liquid absorption system is adapted to prevent liquid in the storage chamber from dropping through the connection port of the liquid storage chamber by means of the liquid retaining force of the porous liquid absorption member thereof.
Next, a liquid jet recording head adapted to be supplied with liquid from an external liquid storage chamber will be discussed below. A liquid jet recording head of this type may be provided with a negative pressure generating means of the liquid absorption type or of the mechanical type or may be adapted to maintain the negative pressure in the liquid jet recording head by means of the water head difference that is produced as a result of the fact that the liquid level in the external liquid storage chamber is lower than the level of the plane of the ejection orifices of the liquid jet recording head.
A liquid jet recording head may be made to eject liquid droplets from its ejection orifices by utilizing thermal energy generated by electro-thermal transducers or by deflecting liquid droplets by means of a pair of electrodes. Liquid jet recording heads adapted to eject liquid droplets by utilizing thermal energy are commercially available and very popular because of the advantages thereof including that liquid ejection orifices for forming liquid droplets that are to be ejected for the purpose of recording can be arranged densely and high resolution images can be formed by this arrangement as well as that the entire head can be made compact with ease.
In ink-jet recording head adapted to eject recording liquid by utilizing thermal energy comprises ejection orifices for ejecting liquid, liquid flow paths communicating to the respective ejection orifices and electro-thermal transducers arranged vis-à-vis the respective flow paths so that it applies ejection energy (e.g., thermal energy for causing liquid to give rise to film boiling) coming from the electro-thermal transducers to the liquid flowing through the liquid flow paths and ejects droplets of liquid through the ejection orifices for a recording operation.
In recent years, ink-jet recording apparatus of various types have been developed and become very popular. Additionally, the recording capacity of such apparatus has been increased so that the consumption of recording liquid is also increasing. As a result, the demand for ink-jet recording apparatus having a large liquid storage capacity has been rising rapidly.
However, liquid jet ejection heads of the above described types (1) through (3), those of the type (1) having a liquid storage chamber as an integral component thereof and those of the type (2) provided with a replaceable liquid storage chamber are accompanied by the problem of a limited capacity of the liquid storage chamber. In other words, the liquid storage chamber or the liquid jet recording head itself has to be replaced frequently to impose a cumbersome replacing operation to the operator (user) particularly when recording liquid is consumed at a high rate. Furthermore, the cost of such consumables is far from negligible.
If, on the other hand, the capacity of the liquid storage chamber is raised, the total weight of the liquid jet recording head increases to raise the inertial force that is produced in the scanning operation of the carriage. Then, there arises a problem that the carriage may not be stable nor reliable for scanning operations to consequently degrade the quality of recording.
Additionally, if the capacity of the liquid storage chamber that is mounted on the carriage is raised, the entire liquid jet recording apparatus may become bulky.
Contrary to liquid jet ejection heads of the above two types, those of the type (3) provided with an external liquid chamber, from which liquid is supplied, are advantageous in that the liquid storage chamber can be placed relatively freely and the recording apparatus is free from becoming bulky if the capacity of the liquid storage chamber is raised.
Additionally, the arrangement of maintaining the negative pressure in the liquid jet recording head by means of the water head difference between the level of the plane of the ejection orifices of the liquid jet recording head and that of the liquid in the liquid storage chamber that is external relative to the head is very simple to provide the advantage of reducing the cost of the apparatus, if compared with the means of producing negative pressure by using a liquid absorption system or a mechanical system.
However, the arrangement of maintaining the negative pressure in the liquid jet recording head by means of the water head difference is also accompanied by the problem, which will be discussed below.
If the liquid jet recording head is subjected to vibrations during transportation and/or unexpected impacts, some of the liquid in the liquid jet recording head can leak out of the head. Generally speaking, if the liquid jet recording head is adapted to eject large liquid droplets having a size greater than 10 pl and its ejection orifices have a large area, the ejection orifices of the liquid jet recording head are covered and protected by a protection tape that seals them when the liquid jet recording head is packed so that no printing liquid may leak out of the ejection orifices. If, on the other hand, the liquid jet recording head is adapted to eject small liquid droplets having a size smaller than 10 pl and its ejection orifices have a small area, the liquid jet recording head can be packed without using a protection tape for sealing the ejection orifices because the printing liquid in the inside is prevented from moving by the high meniscus retaining effect of the ejection orifices. However, with the above packing method of using a tape, the internal pressure of the liquid jet recording head can become very high when it is brought into a situation where the environment can change abruptly due to expansion of the liquid and/or the gas in the liquid chamber of the liquid jet recording head.
Then, if the liquid jet recording head is adapted to eject large liquid droplets and the ejection orifices are covered by a protection tape, the tape can be moved away from the plane of the ejection orifices to allow printing liquid to leak out. Similarly, printing liquid is allowed to scatter from the ejection orifices if the liquid jet recording head is adapted to eject small liquid droplets and the ejection orifices are not covered by a protection tape. Furthermore, liquid will also flow out of the liquid jet recording head if the filler sealing the areas connecting some of the components of the liquid jet recording head is destroyed. Thus, conventional liquid jet recording heads of this type require that the areas connecting some of the components of the liquid jet recording head have to be reliably and hermetically sealed by means of strong fillers so that the head can withstand any abrupt changes in the environment. However, this requirement inevitably results in a high manufacturing cost.
In view of the above identified circumstances, it is therefore the object of the present invention to provide a liquid jet recording head packing method, a liquid jet recording head and a liquid jet recording apparatus equipped with a liquid jet recording head that can effectively suppress the problem of leakage of liquid from the liquid jet recording head due to expansion of the liquid and/or the gas in the liquid chamber when the liquid jet recording head that is provided with a chamber for containing liquid is packed and subsequently subjected to abrupt changes in the environment.
In an aspect of the invention, the above object is achieved by providing a method of packing a liquid jet recording head comprising a plurality of ejection orifices for ejecting liquid droplets, a plurality of flow paths respectively communicating to said ejection orifices, a plurality of energy generating elements arranged respectively vis-à-vis said flow paths and adapted to generate energy for respectively ejecting the liquid in said flow paths from said ejection orifices, a first common liquid chamber arranged upstream relative to said flow paths so as to supply liquid to said flow paths, a liquid supply path for supplying liquid to said first common liquid chamber, a second common liquid chamber arranged upstream relative to said liquid supply path so as to store liquid to be supplied to said liquid supply path, a frame forming said second common liquid chamber and a porous member arranged between said liquid supply path and said second common liquid chamber;
said frame being provided at part thereof with a hole section to be used for pouring liquid into said second common liquid chamber, an elastic peg member being arranged in said hole section so as to block up said hole section, said peg member being provided with a fissure hole, said peg member being so arranged as to allow liquid to be supplied into said second common liquid chamber with a hollow needle member driven into said fissure hole of said peg member in order to supply liquid into said second common liquid chamber;
said method comprising the step of packing said liquid jet recording head while holding a pipe member driven into the fissure hole of said peg member.
With a packing method according to the invention, preferably, the cross section of the peg member as viewed in a direction perpendicular to the central axis thereof is greater than the cross section of the hole section of the frame as viewed in a direction perpendicular to the longitudinal axis thereof, and said pipe member is driven into the fissure hole of said peg member forcibly driven into said hole section of the liquid jet recording head.
Preferably, said pipe member is driven into the fissure hole of said peg member in such a way it is subsequently pushed into said second common liquid chamber by said needle member driven into said peg member and falls from said peg member.
Preferably, said pipe member is made of a resin material or polytetrafluoroethylene.
Preferably, said porous member is filled with liquid at a part thereof located downstream in the sense of supply of liquid while liquid is removed from said porous member at a part thereof located upstream in the sense of supply of liquid when packing said liquid jet recording head.
Preferably, said ejection orifices are tightly sealed by a removable sealing member before removing liquid from said second common liquid chamber when packing said liquid jet recording head.
Preferably, the packing member for packing said liquid jet recording head is made of a material adapted to block permeation of liquid and gas.
In another aspect of the invention, there is provided a liquid jet recording head comprising a plurality of ejection orifices for ejecting liquid droplets, a plurality of flow paths respectively communicating to said ejection orifices, a plurality of energy generating elements arranged respectively vis-à-vis said flow paths and adapted to generate energy for respectively ejecting the liquid in said flow paths from said ejection orifices, a first common liquid chamber arranged upstream relative to said flow paths so as to supply liquid to said flow paths, a liquid supply path for supplying liquid to said first common liquid chamber, a second common liquid chamber arranged upstream relative to said liquid supply path so as to store liquid to be supplied to said liquid supply path, a frame forming said second common liquid chamber and a porous member arranged between said liquid supply path and said second common liquid chamber;
said frame being provided at part thereof with a hole section to be used for pouring liquid into said second common liquid chamber, an elastic peg member being arranged in said hole section so as to block up said hole section, said peg member being provided with a fissure hole, said peg member being so arranged as to allow liquid to be supplied into said second common liquid chamber with a hollow needle member driven into said fissure hole of said peg member in order to supply liquid into said second common liquid chamber;
wherein a pipe member is held in the fissure hole of said peg member.
In still another aspect of the invention, there is provided a liquid jet recording apparatus comprising a carriage adapted to mount a liquid jet recording head thereon and reciprocate, a main tank for storing liquid to be supplied to the second common liquid chamber of said liquid jet recording head, a hollow needle member to be driven into the fissure hole of the peg member of said liquid jet recording head mounted on said carriage to supply liquid from said main tank into said second common liquid chamber and a drive means for driving said needle member so as to push said pipe member held in said peg member into said second common liquid chamber.
A liquid jet recording head to which a packing method according to the invention is applied is mounted on the carriage of a liquid jet recording apparatus main body in such a way that the plane of its ejection orifices is located above the level of the liquid in the liquid storage chamber arranged outside the recording head. The negative pressure of the inside of the liquid jet recording head is maintained by the water head difference between the plane of the ejection orifices of the liquid jet recording head and the level of the liquid in the external liquid storage chamber. Then, as the needle members provided in the liquid jet recording apparatus having such a configuration are driven into the second common liquid chamber respectively through the fissure holes of the corresponding peg members that have been forcibly driven into the respective holes arranged at a lateral side of the second common liquid chamber (auxiliary liquid storage chamber) of the liquid jet recording head, liquid is supplied from the external liquid storage chamber to the liquid jet recording head. Thus, according to the invention, since peg members are provided with fissure holes for holding the pipe members, the needle members can be respectively driven into the fissure holes of the corresponding peg members and pulled out of them without problem. As a result, the load applied to the needle members when they are driven into the peg members and pulled out of them is reduced and hence the liquid jet recording head can be replaced with ease. Additionally, if the center of each of the needle members and that of the corresponding peg member are misaligned relative to each other, the peg member is depressed along the periphery of the fissure hole as the needle member is driven into the peg member from the front end thereof due to the pressure applied to the needle member, so that the front end of the needle member is guided by the fissure hole. In other words, the needle member can reliably be driven into the peg member without requiring a high precision level for the dimensions of both the needle member and the peg member. The operation of driving the needle member is further improved if the fissure hole is branched from the central axis of the peg member at least in three directions.
When packing the liquid jet recording head, the second common liquid chamber is prevented from being completely closed by driving a pipe member into the fissure hole of each of the peg members so as to be held therein. Then, the internal pressure of the liquid jet recording head is prevented from rising extremely if the liquid jet recording head is subjected to an abrupt change in the environment. In other words, if the liquid jet recording head is packed and subjected to an abrupt change in the environment, the risk of liquid leaking from the inside of the liquid jet recording head through the ejection orifices due to unexpected expansion of liquid and/or gas in the liquid chamber is suppressed. Additionally, if the pipe members are held respectively in the fissure holes of the corresponding peg members, the opening of each of the fissure holes is expanded by the corresponding pipe member to reduce the friction that arises when a needle member is driven into the peg member so that the needle member can be driven into the fissure hole with very small driving force.
If each of the peg members is pushed into a hole section whose diameter is smaller than that of the peg member, the fissure hole of the peg member is completely closed by the resiliency of the peg member (compressive force applied to the outer periphery thereof) so that no liquid nor air will leak to the outside through the fissure hole to a great advantage of the liquid jet recording head. Additionally, in a state where a needle member is driven into each of the peg members, the needle member is firmly gripped by the peg member so that again no liquid nor air will leak to the outside. Furthermore, since the pipe members that are driven respectively into the fissure holes of the corresponding peg members at the time of packing are also firmly gripped by the peg members, they are prevented from moving relative to the peg members and eventually coming out from the latter if the liquid jet recording head is subjected to large vibrations and/or impacts. Therefore, the pipe members are reliably held by the peg members if they are made very short to reduce the cost of the pipe members.
Additionally, as a porous member that shows a large pressure loss is provided, the liquid found in the flow path where the energy generating elements are arranged, the first common liquid chamber and the liquid supply path, which are located downstream relative to the porous member, can hardly move. Therefore, a situation in which liquid flows from this region into the second common liquid chamber through the porous member will hardly take place. Furthermore, when the ejection orifices are hermetically sealed by a sealing member, problems involving no liquid ejection will be prevented from occurring, because printing liquid is prevented from drying at and near the ejection orifices and any of the ingredients of printing liquid is prevented from adhering to and near the energy generating elements.
Finally, when mounting the liquid jet recording head on the liquid jet recording head and subsequently driving the needle members into the respective peg members, the front ends of the needles members push respectively the corresponding pipe members until the pipe members are released from the peg members and forced to fall into the second common liquid chamber. Thus, the operator does not need to pull out the pipe members when installing the liquid jet recording head.